1. Field of the Invention
The present invention relates generally to internal combustion engines and, more specifically, to a method of predicting the volume of finished combustion chambers from a raw cylinder head casting for an internal combustion engine.
2. Description of the Related Art
It is known to cast a cylinder head for an internal combustion engine. The cylinder head has at least one, sometimes a plurality of combustion chambers. The raw cylinder head casting is typically finished by machining the deck face and valve seat surfaces to prepare it for installation of spark plugs and valves.
It is also known that variations in the volume of the combustion chamber have a strong effect on the variation of the compression ratio of each cylinder. Differences in compression ratio between cylinders of the same engine lead to engine noise vibration harshness (NVH). Differences in compression ratio among engines of the same family require using a less than optimum engine calibration for the engine, in order to meet emissions, which reduces power and adversely affects fuel economy. Thus, it is desirable to know and control the volume of a combustion chamber for a finished cylinder head.
The most common method for measuring the volume of a combustion chamber is to first perform the finish machining and then measure the volume of liquid required to fill the chamber. The method involves covering the combustion chamber with a glass plate having a small hole therethrough. The combustion chamber is carefully filled with liquid, which is accurately measured. Another method uses sonic resonance to compare a test chamber to a master chamber. Both of these methods only measure the volume of combustion chambers and are laborious and lack repeatability. Further, neither of these methods will work with a cylinder head as casted, since they require a totally enclosed volume, i.e. the combustion chamber must contain both valves and spark plug. By knowing the finished volume at the time of casting, it is possible to adjust the casting process to repeatably produce the desired volume. Thus, there is a need in the art to predict the volume of a finished combustion chamber from a raw cylinder head casting.